MOD-WIFI-ESP8266-DEV is a development board for the ESP8266 WiFi SoC. All GPIOs and resources are exposed in both through-hole and stamp-hole interfaces, so you can use it with a breadboard or solder it to a PCB. A W25Q16B SPI Flash memory IC is already provided to run the SoC. The board has a PCB trace antenna as well as a U.FL connector in case you want to use an external antenna.

Solder jumpers allow you to choose which antenna option to use, and to do some I/O configuration (refer to the schematic for details).

There also are pads where you could install a UEXT connector, but if UEXT is what you're after, you might consider the MOD-WIFI-ESP8266 which has a UEXT connector already installed (but does have the through-hole or stamp-hole interfaces).

Evaluation Board Available

If you want a ready-made evaluation board, consider the ESP8266-EVB, which includes this module plus a host PCB with a relay, a button, a UEXT connector, a power input jack, and GPIO headers.

Espressif ESP8266 Features

The ESP8266 is very highly integrated SoC that includes an Xtensa LX106 core processor, RAM, and RF front-end allowing a WiFi TCP/IP stack to be implemented on board with just a few components. Since it found its way to the English-speaking world in the fall of 2014 it has attracted a lot of attention — there's even an Arduino IDE for it now. Its features include: